Diffusion-weighted imaging and diagnosis of transient ischemic attack

Area of Science:

• Neurology
• Radiology
• Medical Imaging

Background:

• Magnetic resonance (MR) diffusion-weighted imaging (DWI) is a sensitive tool for detecting small acute ischemic lesions.
• Its utility in diagnosing transient ischemic attack (TIA) is recognized, with ongoing discussions about reclassifying DWI-positive TIA cases as stroke.

Purpose of the Study:

• To assess the positivity rate of DWI in patients diagnosed with TIA.
• To evaluate the implications of DWI findings for the potential reclassification of TIA as stroke.

Main Methods:

• A systematic literature search was conducted from January 1995 to July 2012, adhering to PRISMA guidelines.
• Studies included patients presenting with suspected TIA who underwent MR DWI and reported acute DWI lesion proportions.
• Univariate random-effects meta-analysis was used to determine DWI-positive rates and identify influencing factors.

Main Results:

• The meta-analysis included 47 studies with 9,078 patients; 55% of diagnoses were confirmed by stroke specialists.
• The pooled proportion of TIA patients with acute DWI lesions was 34.3% (95% CI: 30.5-38.4%).
• Larger studies reported lower DWI-positive rates (29%) compared to smaller studies (40.1%), with no other factors explaining the significant variation in DWI positivity.

Conclusions:

• Negative DWI scans are the most common finding in patients with definite TIA.
• The reasons for negative DWI findings in approximately two-thirds of TIA patients remain unclear.
• Reclassifying DWI-positive TIAs as strokes without understanding these factors may increase variance in global stroke and TIA burden estimates.